1. Field of the Invention
This invention relates to cellular polymers and intermediates therefor and is more particularly concerned with novel polyol blends and their use in a process for the preparation of cellular polyisocyanurates.
2. Description of the Prior Art
Cellular polyisocyanurate polymers are well known in the art for their use in various types of thermal insulating applications. They are also well known for their ability to withstand heat and flame; see U.S. Pat. Nos. 3,745,133, 3,986,991, and 4,003,859. Minor amounts of polyols are sometimes added to the foam forming ingredients to modify the foam properties. When fluorocarbon blowing agents are employed the problem of the incompatibility that may arise between the polyol, particularly primary hydroxyl polyols, and fluorocarbon in resin premixes is generally solved by premixing most, if not all, the fluorocarbon with the polyisocyanate; see the patents cited supra.
Polyisocyanurate foams find particular utility in the production of laminated foam board stock material which can be prepared with a variety of different facer materials. Problems which can arise in the production of such laminate material include (1) lack of uniform foam core strength; (2) poor adhesion between foam core and facer material; (3) maintaining good fire resistance in the foam; and (4) keeping foam friability at low levels. These problems have been overcome in the art by employing minor amounts of low equivalent weight polyols, particularly diols, in the formulation, combined with the heating of the formed laminate product in an oven at 160.degree. to 190.degree. F.; see U.S. Pat. No. 3,903,346.
However, the low equivalent weight polyols employed, particularly the preferred diols (see column 4, lines 59-61 of U.S. Pat. No. 3,903,346) having only primary hydroxyl groups, cannot be blended beforehand with the fluorocarbon blowing agent in a "B" side component because of the low solubility of the diol-fluorocarbon pair. This necessitates the blending of the fluorocarbon with the polyisocyanate in the "A" side component. Further, because of the fluorocarbon diol immiscibility, the above patent teaches that a third component "C" is required which contains the catalyst constituent dissolved in a low molecular weight glycol; see column 2, lines 32-33 and the examples of U.S. Pat. No. 3,903,346.
Furthermore, a laminate prepared in accordance with the patent noted above must be heated in an oven to provide a product having a uniform foam core strength.
Surprisingly, it has been found that high levels of fluorocarbon blowing agent are completely miscible with low molecular weight polyols containing primary hydroxyl groups when novel blends comprising a certain type of amine triol with the primary hydroxyl polyols are employed. Additional ingredients which can be present in the miscible blends are surfactants, catalysts, and the like.
U.S. Pat. No. 2,956,031 discloses the use of minor amounts of diamine triol compounds in combination with polyols in general as a means for obtaining highly cross-linked water blown polyurethane foams. However, this reference does not comprehend or indirectly disclose the novel miscible blends of fluorocarbon, low molecular weight primary hydroxyl polyols, and diamine triols in accordance with the present discovery. Also, the prior art does not disclose the proportions of ingredients required to achieve the high levels of fluorocarbon solubility presently observed (see Example 3 below).
Further, it has been found that the same type of miscible primary hydroxyl containing blends as described above, except that water replaces the fluorocarbon component, can be obtained.
Furthermore, it has been discovered that the novel polyol blends above can be employed in minor amounts as a B type component to prepare polyisocyanurate foams characterized by low friability, fine cell structure, good dimensional stability, and low flame spread, via a two-component, i.e., and A, and a B side, process. The fluorocarbon and water components act as the blowing agents in their respective foam forming formulations.
Further, the amine triol referred to above can be employed as the sole polyol ingredient in combination with the fluorocarbon or water, catalyst, surfactant, and other adjuvants to provide polyisocyanurate foams in accordance with the present invention.
Quite unexpectedly, the presence of the amine triol in the B side gives rise to excellent reactant compatibility between the polyisocyanate and the other ingredients. This gives rise in turn to faster reactivity compared to prior art foams and very good reaction exotherm. The high exotherm is of particular advantage when foam laminates are being prepared because it results in excellent adhesion between foam and facer material thereby eliminating the need of heating the formed laminate in an oven.